/*
 * Copyright 2014-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package de.codecentric.boot.admin.client.registration;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.LongAdder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Registers the client application at spring-boot-admin-server
 */
public class ApplicationRegistrator {
    private static final Logger LOGGER = LoggerFactory.getLogger(ApplicationRegistrator.class);
    private final ConcurrentHashMap<String, LongAdder> attempts = new ConcurrentHashMap<>();
    private final AtomicReference<String> registeredId = new AtomicReference<>();
    private final ApplicationFactory applicationFactory;
    private final String[] adminUrls;
    private final boolean registerOnce;
    private final RegistrationClient registrationClient;

    public ApplicationRegistrator(ApplicationFactory applicationFactory,
                                  RegistrationClient registrationClient,
                                  String[] adminUrls,
                                  boolean registerOnce) {
        this.applicationFactory = applicationFactory;
        this.adminUrls = adminUrls;
        this.registerOnce = registerOnce;
        this.registrationClient = registrationClient;
    }

    /**
     * Registers the client application at spring-boot-admin-server.
     *
     * @return true if successful registration on at least one admin server
     */
    public boolean register() {
        Application application = this.applicationFactory.createApplication();
        boolean isRegistrationSuccessful = false;

        for (String adminUrl : this.adminUrls) {
            LongAdder attempt = this.attempts.computeIfAbsent(adminUrl, k -> new LongAdder());
            boolean successful = register(application, adminUrl, attempt.intValue() == 0);

            if (!successful) {
                attempt.increment();
            } else {
                attempt.reset();
                isRegistrationSuccessful = true;
                if (this.registerOnce) {
                    break;
                }
            }
        }

        return isRegistrationSuccessful;
    }

    protected boolean register(Application application, String adminUrl, boolean firstAttempt) {
        try {
            String id = this.registrationClient.register(adminUrl, application);
            if (this.registeredId.compareAndSet(null, id)) {
                LOGGER.info("Application registered itself as {}", id);
            } else {
                LOGGER.debug("Application refreshed itself as {}", id);
            }
            return true;
        } catch (Exception ex) {
            if (firstAttempt) {
                LOGGER.warn(
                    "Failed to register application as {} at spring-boot-admin ({}): {}. Further attempts are logged on DEBUG level",
                    application,
                    this.adminUrls,
                    ex.getMessage()
                );
            } else {
                LOGGER.debug(
                    "Failed to register application as {} at spring-boot-admin ({}): {}",
                    application,
                    this.adminUrls,
                    ex.getMessage()
                );
            }
            return false;
        }
    }

    public void deregister() {
        String id = this.registeredId.get();
        if (id == null) {
            return;
        }

        for (String adminUrl : this.adminUrls) {
            try {
                this.registrationClient.deregister(adminUrl, id);
                this.registeredId.compareAndSet(id, null);
                if (this.registerOnce) {
                    break;
                }
            } catch (Exception ex) {
                LOGGER.warn(
                    "Failed to deregister application (id={}) at spring-boot-admin ({}): {}",
                    id,
                    adminUrl,
                    ex.getMessage()
                );
            }
        }
    }

    /**
     * @return the id of this client as given by the admin server.
     * Returns null if the client has not registered against the admin server yet.
     */
    public String getRegisteredId() {
        return this.registeredId.get();
    }


}
